When the leaves have fallen, and temperatures drop below freezing, many mariners store their boats for the winter. Before putting your boat in storage, it’s important to understand how to store your boat batteries for the winter. Protocols can vary depending on the climate where your boat is and the type of marine batteries you own. There are a variety of things to consider before you decide whether to leave your batteries in for the winter. 

Maintaining Marine Batteries Through the Winter 

Anyone who’s owned a battery knows they aren’t immune to the elements. All varieties of batteries will be affected by extreme temperatures to some extent. Both traditional starting batteries and deep cycle house batteries can be damaged if not properly stored in the winter.  

There are few things more disappointing than arriving at the marina, ready to use your boat, only to find a dead battery. Whether the dead battery simply needs to “wake up” or it requires full repair or replacement, this can be avoided. It’s crucial to ensure your boat and batteries are stored and maintained properly all year round. This will give you peace of mind at the start of next season.

What Happens If Your Marine Batteries Freeze?

Have you ever heard that storing your batteries in the freezer will make them last longer? Although this may sound unusual to those familiar with battery chemistry, there has long been folklore surrounding placing generic household batteries in the freezer to extend their life. While the effectiveness of this practice on AA, AAA, C, and D batteries remains to be seen, one thing is clear: you absolutely should not put your boat, RV, or car battery in the freezer.  

Although it’s uncommon, there are certain conditions that can cause lead-acid marine batteries to freeze completely. This can happen when the lead acid battery is nearly entirely drained of power. At this point, a chemical process is activated that dilutes the liquid electrolyte in the batteries.  

Since the diluted electrolyte has a much higher water content which is more prone to freezing. If the diluted electrolyte begins to freeze, it can damage the battery cells and the battery case due to expansion. Different types of lead-acid batteries will have different freezing points, but all are adversely affected by cold weather.  

In contrast to lead-acid batteries, lithium-ion batteries are less impacted by cold weather and will not freeze under most conditions. In fact, Battle Born LiFePO4 Batteries won’t experience any negative operating effects until conditions reach subzero temperatures.   

Can You Leave Marine Batteries on Your Boat in Freezing Temperatures? 

Although the ability to leave your batteries in your boat will depend heavily on the weather, it’s generally not recommended to leave them in freezing temperatures. Extreme cold can lead to a cracked or entirely drained lead-acid marine battery. You may need to make regular trips to your boat during winter to perform maintenance and ensure your battery remains operational. 

Additionally, when using traditional lead-acid batteries, a battery maintainer can be used when leaving your batteries for extended periods of time. A battery maintainer will keep a low, constant charge on your batteries, which can prevent them from freezing. This slow trickle charge provides just enough constant energy to counteract the natural energy loss incurred by cold weather. Battery maintainers also include smart technology to prevent the batteries from overcharging or entering other unsafe operating conditions. Even when leaving batteries in a boat connected to a battery maintainer, always disconnect them from the boat’s wiring. 

Removing and Storing Your Marine Batteries for the Winter

At a minimum, when not in use, you should always disconnect your batteries from the electrical system on your boat. Oftentimes, a battery disconnect switch within your electrical system is an easy way to cut power to your batteries. These switches cut off most loads while essential systems (like emergency sensors or carbon monoxide alarms) can still draw power. This is why it’s important to fully disconnect marine batteries during periods of extended inactivity. In return, you can avoid a slow and steady draining of energy. 

The best way to store marine batteries during the winter is to completely remove them from your boat and store them somewhere they won’t encounter below-freezing temperatures. This will help ensure your batteries remain at proper temperatures throughout the winter and stay safe from any potential severe weather. Additionally, removing your batteries gives you the option to place them somewhere it is easy to keep a battery maintainer on them. Keep in mind that lead-acid batteries can off-gas, even when disconnected, and need to be stored in a well-vented area and not in the living space. 

On the other hand, while lead-acid batteries are more sensitive to cold weather, Battle Born lithium marine batteries are much more robust. In most winter conditions, we recommend fully charging your batteries and using the battery disconnect switch when you’re away from your boat. However, if temperatures are expected to be below -15℉, we recommend removing your batteries and keeping them in a climate-controlled location. They can be stored anywhere indoors because they are non-toxic, fully sealed, and do not off-gas. 

Charging Marine Batteries During the Winter 

To ensure your boat will be ready to use in the spring, it’s crucial to know how to keep your batteries charged over the winter. If you are using traditional lead-acid batteries, leaving them without charge, especially in cold temperatures, can cause permanent damage and shorten the life of your batteries. A battery maintainer can be used to help prevent damage and keep your batteries in optimal operating condition.  

Although lead-acid batteries need assistance maintaining their charge, lithium batteries generally don’t experience a major loss of energy over time. In fact, if kept above subzero temperatures, Battle Born LiFePO4 batteries will only experience a 2-3% loss of charge per month of storage. This allows them to be stored for winter fully disconnected and without a battery maintainer. 

If your batteries encounter extreme cold temperatures or are left for an extended period of time, they may need to be completely recharged. We recommend bringing the batteries to a temperature above freezing before attempting to charge them. Charging batteries at below-freezing temperatures can damage them and reduce their lifespan. This will also be helpful if you have Battle Born lithium batteries. Their BMS prevents charging if the internal temperature is too low. So, they will need to be brought to a temperature above 25°F to recharge. 

Winter Storage Recommendations for Battle Born Batteries 

Battle Born Batteries offer an easy winterizing process. Simply bring the battery to a full charge and then disconnect it from the electrical system. If you’re in a milder climate, it is safe to leave your batteries in the boat during storage. However, this is not the case for those whose boats could experience subzero temperatures where they are stored. In these scenarios, we recommend removing them and storing them somewhere dry and temperature-controlled. While in storage, Battle Born Batteries will typically lose just 2-3% of their charge per month. Even after six months, your batteries should still have 75-80% of their capacity remaining.  

Charging, maintaining, and storing boat batteries for the winter shouldn’t be a complicated process. However, it can be a crucial step in having a working power system in the spring. Follow these simple guidelines, and your boat’s marine battery will make it through the winter safely. 

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